Conventionally, as a tip dresser for dressing an electrode tip used for a spot welding, there exists the tip dresser that fixes a cutter to a rotating holder and cuts a top of an electrode tip.
FIG. 4 is a section drawing showing a state of an electrode tip being cut by a conventional tip dresser.
For example, as shown in FIG. 4, a tip dresser is known where a cutter 110 is fixed by a screw to a holder 100 having concave taper faces 101 on both upper and lower faces. With respect to the tip dresser, an edge portion 111 of the cutter 110 slightly protrudes from surfaces of the taper faces 101; if the holder 100 is rotated, the edge portion 111 is configured to always contact ends or corners of electrode tips 120.
But because the cutter 110 is only disposed at one place in circumferential directions of the taper faces 101, there exists, for example, a problem that: if the electrode tips 120 are attached slantingly with respect to a rotation axis (not shown) and tops of the tips 120 are displaced from the rotation axis of the holder 100, the tips 120 continue on radially swinging and a place swinging outward is excessively cut and the tips 120 are dressed into distorted forms.
Therefore, as a tip dresser for preventing the radial runnout of an electrode tip, the tip dresser is also known where two cutters are provided symmetrically to the rotation axis of a holder.